The purpose of this project is to culturally adapt an established evidence-based treatment, Relapse Prevention (RP), and pilot-test the resulting Indigenist Relapse Prevention (IRP) intervention on the Fort Peck Indian Reservation in rural Montana. The research team will work with its existing community partners from the Assiniboine and Sioux Tribes within a community-based participatory research (CBPR) framework to carry out the study aims. The team will collaboratively modify existing RP strategies using an iterative cultural adaptation process to address specific cultural factors identified by previous research and enhance social validity. These efforts will result in a culturally appropriate intervention for American Indians (AIs) with substance use disorder that is practical, easily replicable, and acceptable to the community. This work is necessary before the team can successfully implement the adapted IRP intervention and test its efficacy on a broader scale, which is the intended goal of a future R01 grant proposal. The proposed pilot study will be conducted with Fort Peck tribal members with substance use disorder who are motivated to change and have an abstinence goal (n = 40). The research team will use a randomized block design with assignment to a treatment condition or a wait-list control condition and repeated assessments of substance use behavior. The pilot study will allow the team to identify barriers to successful implementation of the intervention as well as threats to internal validity that it must account for in future research. The research team also will gain 1) experience training paraprofessionals to administer the intervention with fidelity, 2) increased understanding of effective and culturally appropriate study methods, and 3) crucial preliminary data on the psychometric properties of the team's instruments and estimates of effect size for power calculations. The research team will use this information to support a future R01 grant application to test the efficacy of the culturally adapted IRP intervention for rural AIs with substance use disorder. The short-term goal of this research is to develop a successful relapse prevention intervention for AIs that is practical, easily replicated, and administered by trained lay community health advisors. The long- term goal is to disseminate the intervention by incorporating it into existing treatment programs to ensure local sustainability and broader utilization by other tribal communities nationwide.